In recent years, along with progress of the lithography technique, a resist pattern formed during a manufacturing process of a semiconductor device or a liquid crystal device has been micronized. As a method for micronization, irradiation light has been shortened in wavelength. To be specific, ultraviolet ray typified by g-ray (wavelength 438 nm) or i-ray (wavelength: 365 nm) of the related art has been replaced by DUV (Deep Ultra Violet) having a shorter wavelength.
Recently, a KrF excimer laser (wavelength: 248 nm) lithography technique has been introduced as a DUV lithography technique, and an ArF excimer laser (wavelength: 193 nm) lithography technique and an EUV (wavelength: 13.5 nm) lithography technique, which are intended to realize shorter wavelength, have been studied. Further, a liquid immersion lithography technique has also been studied. Furthermore, as a lithography technique, which is different from the above techniques, an electron beam lithography technique has been studied.
As a high sensitivity resist composition used for forming a resist pattern by a DUV lithography technique or an electron beam lithography technique, a “chemically amplified resist composition” containing a photoacid generator has been improved and developed.
For example, as a chemically amplified resist material used for an ArF excimer laser lithography technique, an acrylic polymer, which is transparent to light having a wavelength of 193 nm has received great attention. As an acrylic polymer, for example, a copolymer of a (meth)acrylic acid ester having an adamantane backbone in an ester moiety and a (meth)acrylic acid ester having a lactone backbone in an ester moiety has been suggested (Patent Documents 1 and 2, and the like)
However, when the acrylic copolymer is used as a resist copolymer, a shape of a resist pattern to be formed is not necessarily favorable, and dry etching resistance after the resist pattern is formed is not sufficient to suppress the surface roughness of a pattern formed when a dry etching is carried out using the resist pattern as a mask and a substrate is processed, and, thus, improvement in these properties has been demanded.
Further, Patent Document 3 discloses a copolymer that contains a cyano group in two or more kinds of constituent units containing a lactone backbone, and Patent Document 4 discloses a copolymer containing a constituent unit that contains a cyano group in a norbornane backbone, and Patent Documents 3 and 4 also describe that performance of lithography is improved by applying these copolymers.